The present invention relates to a continuous temperature variance pyrolysis process and apparatus for recovering valuable oil products, carbon black, steel, and uncondensed vapors from tire chips.
Over the past few decades the growth of illegal tire dumps has become a major environmental and health problem. Waste tires are generated in the United States at an estimated rate of approximately 240 million tires per year. Of the 240 million waste tires, approximately 200 million are estimated to be land filled or stockpiled. However, the very characteristics that ensure durability of the tires also make their disposal difficult whereby discarded tires can last between 500 to 1000 years in the environment. Therefore, these tires pose a unique landfill problem. In addition to becoming breeding grounds for countless varieties of vermin and mosquitoes, discarded tires are known to xe2x80x9cfloatxe2x80x9d to the surface, exerting sufficient force to rupture the landfill cap. Moreover, piles of discarded tires, such as those existing at numerous sites around the world, can serve as fuel for sustaining combustion once the piles are somehow set ablaze, such as by lightning or by accidental or purposeful human agency.
In order to prevent such major environmental hazards, increasingly the waste tires have been shredded into more manageable tire chips. While some companies continue to burn the whole tire for fuel, many others use the tire chips to fuel other processes. However, with the utilization of these methods, valuable byproducts such as carbon black are needlessly wasted. Moreover, gas emissions from the burning process can prove harmful to the environment.
One economically feasible and environmentally effective means for disposing of the tire chips is through the process of pyrolysis. The tire chips can be pyrolized to yield saleable products including gases, useful oil and carbon black.
Pyrolysis is the process of utilizing heat to cause a chemical change in a substance. In particular, the actual pyrolysis process is the result of the heat-induced chemical decomposition of organic materials in the absence of oxygen. Saturating the chips with process oil effectively facilitates the pyrolysis to yield pyrolytic gas, oil, and a char-steel mixture. The char is a fine particulate matter composed of carbon black, char and other inorganic materials, such as zinc oxide, carbonates and silicate.
Pyrolysis is especially appealing for tire chip disposal because each product and by-product of the pyrolytic process is marketable. The generated gas has a heat value of from about 170 to 2,375 BTU/ft3. The produced light oils can be sold for gasoline additives to enhance octane, and the heavy oils can be used as a replacement for number six fuel oil. The solid char can be upgraded and sold as carbon black.
Pyrolysis poses little to no harm to the environment because of the absence of harmful emissions. However, upgrading char to carbon black and the pyrolytic process itself can prove expensive. Moreover, tire pyrolysis can prove economically detrimental if an efficient process is not utilized to produce a sufficient amount of product yield. Examples of such systems are disclosed in U.S. Pat. No. 4,983,278 issued Jan. 8, 1991 to Cha et al.; U.S. Pat. No. 5,389,691 issued Feb. 14, 1995 to Cha et al.; and U.S. Pat. No. 4,647,443 issued Mar. 3, 1987 to Apffel.
Accordingly, there continues to be a need in the industry for improvements in the effective pyrolytic disposal of tire chips.
The present invention discloses an apparatus and process for pyrolyzing waste tire chips to extract carbon black oil, and various gases. The tire chips are fed into an inclined rotary kiln and exposed to heat at continuously varying temperature as the tire chips move through the kiln. Within the kiln, the tire chips are soaked in oil such that a chemical reaction occurs, resulting in a dry solid product and a gaseous, vapor product. The solid product is subsequently fed through a magnetic separator which separates the steel from the remaining char. The char can then be upgraded to yield carbon black.
The gaseous product stream passes through multiple condenser/scrubbers to yield a purified form of oil for storage, char for conversion into carbon black, and uncondensed gas used as fuel for the kiln.